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<DIV><FONT size=3D2>The recent comments on ball bearings have bee=
n=20
interesting. The comment from David that 'his' ball bearings had open sides=
=20
reminded me of an inspection of a tower structure by a member of =
the=20
Towers & Belfries Committee in (I think) a Derbyshire tower. It wa=
s=20
pointed out to him that all the bells had been fitted with ball bearings. T=
o=20
his quite reasonable surprise he found that ordinary ball bearing race=
s had=20
been fitted onto the gudgeons and that the races themselves were held =
onto=20
the frame by a flat-section inverted 'U' straps. The balls themselves=
=20
were fully exposed. The local ringer there was very proud of the=20
conversion. This had clearly been done on a DIY basis and clearly without t=
he=20
knowledge of the Diocesan authorities and a faculty.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>If David's bearings are anything like this, he nee=
ds to=20
be worried. Firstly, ball bearings are manufactured to extremely =
fine=20
tolerances and any grit entering the bearing (as the above=20
arrangement) will very soon destroy the bearing. Secondly, the grease =
is=20
there in part to allow the balls to slide against each other or against the=
=20
cage, but more so to prevent corrosion in the surfaces; and this is the rea=
son=20
for using non-acidic grease. Should this type of grease be in con=
tact=20
with air, it will soon oxidise, go hard and be rendered useless. =
That=20
is another reason why ball bearing housings are sealed. Thirdly, =
ball=20
bearings used for bells are self-aligning, ie they can accommodate a=20
certain degree of angular movement of the gudgeon, which arises from irregu=
lar=20
movement of frame sides, for instance. An ordinary bearing cannot do t=
his=20
and will soon wear out if used in such circumstances. Fourthly, ball bearin=
gs=20
for bells are given end float in one of the housings, to accommodate=20
longitudinal movement in the gudgeon (from frame sides that move towar=
ds=20
and away from each other). If there is no end float, the bearings will=
=20
become axially-loaded and the bell can be harder to swing because of t=
his.=20
Mears & Stainbank housings for single-row ball bearings=20
initially failed to provide for end float. Lastly, bell bearings have =
to=20
withstand 4 times the deadweight when the bell is rung full circle. A 5cwt =
bell=20
will exert 1 ton downwards as it revolves. The bearings need to be sized fo=
r=20
that loading, otherwise (again) wear will occur. G&J's ball bearing wer=
e=20
always on the small size. Alan Hughes told me they always change the bearin=
gs=20
when they refurbish G&J-hung bells. Wooden bellframes tend to move=
=20
around more than metal frames, so the self-aligning facility is very import=
ant.=20
The end-float is similarly important with wooden frames, although temperatu=
re=20
variations in metal frames and fittings can produce similar=20
results.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>To get some historical aspects into this subject, it ma=
y be=20
interesting to know that when ball bearings were metrically sized=
=20
(generally Swedish: SKF) when initially used for bells. The Briti=
sh=20
ball bearing industry then produced imperially sized bearings and these=20
were used. The metric revolution of the 70's encouraged the use of met=
ric=20
bearings world-wide and imperially-sized bearings were gradually phase=
d=20
out. The bell industry started to used metric bearings again. I unders=
tand=20
that SKF no longer produce imperially-sized bearings. Imperially-sized bear=
ings=20
are now comparitively difficult to obtain and expensive compared to their m=
etric=20
counterparts, which is bad news for those towers that have such bearings an=
d=20
where they have become worn (yes, ball bearings do wear out, even with=
the=20
correct maintenance - which is do nothing to them). However, those towers=20
that had early ball bearing use are still very well catered for,=
=20
because metric bearings are cheap and plentiful. It is a myth that the Amer=
ican=20
ball bearing industry produces imperially-sized bearings in vast quantities=
. The=20
Americans woke up to the fact many years ago that if they were produci=
ng=20
goods to go all over the world - particularly vehicles - the breakdown of a=
n=20
imperial bearing in, say, some Third World country would be catastroph=
ic=20
for future sales, as it would mean the vehicle would be laid-up until an=20
imperial bearing could be shipped out. Far better to use metric bearings, w=
hich=20
would be stocked at the local garage or bearing supplier. I understand the=
=20
Americans just measure their bearings imperially.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>The double-row self-aligning SKF bearings at Evesham di=
d 43=20
years before most of them were either badly worn or becoming so. Singl=
e-row=20
self-aligning bearings generally last much longer, because there is more=20
metal-to-metal contact with the balls, but this type of bearing suffer=
s=20
from fretting between the self-aligning collar and the outer bearing race. =
The=20
double-row self-aligning type is (I think) used universally now. The intere=
sting=20
aspect of worn ball bearings is that the bell continues to ring well, unlik=
e=20
worn plain bearings, which affect go straightaway. Worn ball bearings =
emit=20
rumbling noises; the louder the noise, the greater the wear. A ball-bearing=
ed=20
bell only starts to go badly when the bearing is very badly worn, such that=
the=20
wear has allowed the gudgeon to drop sufficiently to rub on the housing. I=
=20
suspect there are a lot of worn ball bearings out there, but they are undet=
ected=20
because the bells are still going well - and it's very difficult to hear th=
e=20
rumbling above the ringing.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>There was a lot of correspondence in RW in the early/mi=
d 1940s=20
about the merits of ball bearings and plain bearings. Some ringers thought =
ball=20
bearings were harder to ring on than properly-lubricated plain ones in=
good=20
condition. Because the oil film in plain bearings reduces when the bell sto=
ps at=20
mouth-up, it allows the bell to 'sit' at the balance, rather than having to=
hold=20
the bell at the balance as with ball bearings. Most of us have either been=
=20
taught on ball bearinged bells or become used to them, so the 'sitting' of=
=20
plain-bearinged bells has less significance. The greater difficulty of=
=20
ringing slowly with ball bearings has, of course, led to faster ringing, ie=
not=20
up to the balance. The problem now appears to be getting ringers not used t=
o=20
plain bearings to ring slowly on plain bearings to take advantage of t=
he=20
'sit'.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Chris Povey</FONT></DIV></BODY></HTML>